Underwater sampling and mapping apparatus

ABSTRACT

The present application provides a system, method and apparatus for measuring at least one physical and/or chemical variable at a plurality of different locations within a body of water. The method includes the steps of: providing dynamic measurement means configured to measure the at least one physical and/or chemical variable; towing said measurement means in said body of water at a predetermined depth, and simultaneously taking measurements of least one physical and/or chemical variable, at least periodically, and generating measurement data; and determining the location of the measurement means while taking said measurements of the at least one physical and/or chemical variable and generating corresponding location data. A method for mapping at least one physical and/or chemical variable for a body of water is also disclosed.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for performingmulti-variable mapping of bodies of surface water.

BACKGROUND OF THE INVENTION

It is now clear that human activity can have a great impact on theenvironment. As a result of this realisation, an environmental impactstatement or environmental assessments are often made before adevelopment is begun. The appreciation of the potential for human impacton the environment may also lead to an increase in research andenvironmental modelling in order to determine the, mechanisms for, andeffects of, human activity on the environment.

In order to increase the speed, quality, accuracy and cost effectivenessof environmental assessment, environmental monitoring and base linesurveying improved techniques and systems for measuring physicalvariable in the environment are desired.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amethod for measuring at least one physical and/or chemical variable at aplurality of different locations within a body of water, said methodincluding the steps of:

providing dynamic measurement means configured to measure the at leastone physical and/or chemical variable;

towing said measurement means in said body of water at a predetermineddepth, and simultaneously taking measurements of least one physicaland/or chemical variable, at least periodically, and generatingmeasurement data; and

determining the location of the measurement means while taking saidmeasurements of the at least one physical and/or chemical variable andgenerating corresponding location data.

Preferably the method includes the additional the step of:

controlling the depth of the measurement means in said body of waterwhilst towing said measurement means.

Preferably the method includes the additional the step of:

detecting obstacles in a region adjacent to said measurement means; and

wherein the step of controlling the depth of said measurement means isperformed in response to detected obstacles.

Preferably the step of, detecting obstacles in a region adjacent to saidmeasurement means, includes the sub-steps of:

providing image capture means on said measurement means, adapted togenerate a sequence of images of a region adjacent to said measurementmeans; and

visually detecting said obstacles from said sequence of images.

Preferably said measurement means includes water intake means configuredto collect water from said body of water and wherein said methodincludes the additional step of:

collecting at least one water sample from said body of water throughsaid water intake means.

Preferably the predetermined depth is determined relative to a bottom ofthe body of water.

Preferably water depth and at least one other physical and/or chemicalvariable is measured by said measurement means.

Preferably the at least one physical and/or chemical variable measuredby the measurement means is selected from a list including the followingphysical and chemical variables:

water depth, water temperature, conductivity, and water turbidity, pH,dissolved oxygen, dissolved chloride, oxidation-reduction potential(ORP), soluble nitrate, ammonia, dissolved gases or chlorophyll A.

According to a second aspect of the present invention there is provideda method of mapping at least one physical and/or chemical variable inbody of water, said method including the steps of:

providing dynamic measurement means configured to measure the at leastone physical and/or chemical variable; and

towing said measurement means in said body of water at a predetermineddepth, and simultaneously taking measurements of said at least onephysical and/or chemical variable, at least periodically, and generatingmeasurement data;

determining the location of the measurement means while taking saidmeasurements of the at least one physical and/or chemical variable andgenerating corresponding location data; and

generating a map representative of the distribution of the at least onephysical and/or chemical variable within said body of water on the basisof the location and measurement data.

Preferably the method additionally includes the additional the step of:

determining the depth of the measurement means when measuring said atleast one physical and/or chemical variable, and generating measurementdepth data, and wherein said map is generated on the basis of themeasurement depth data, measurement data and location data.

Preferably the method includes the additional the step of:

controlling the depth of the measurement means in said body of waterwhilst towing said measurement means.

Preferably the method includes the additional the step of:

detecting obstacles in a region adjacent to said measurement means; and

wherein the step of controlling the depth of said measurement means isperformed in response to detected obstacles.

Preferably the step of, detecting obstacles in a region adjacent to saidmeasurement means, includes the sub-steps of:

providing image capture means on said measurement means, adapted togenerate a sequence of images of a region adjacent to said measurementmeans; and

visually detecting said obstacles from said sequence of images.

Preferably said measurement means includes water intake means configuredto collect water from said body of water and wherein said methodincludes the additional step of:

collecting at least one water sample from said body of water throughsaid water intake means.

Preferably the predetermined depth is determined relative to a bottom ofthe body of water.

Preferably water depth and at least one other physical and/or chemicalvariable is measured by said measurement means.

Preferably the at least one physical and/or chemical variable measuredby the measurement means is selected from a list including the followingphysical and chemical variables:

water depth, water temperature, conductivity, and water turbidity, pH,dissolved oxygen, dissolved chloride, oxidation-reduction potential(ORP), soluble nitrate, ammonia, dissolved gases or chlorophyll A.

Preferably the map represents topographic contours of a bottom of thebody of water and the distribution of the at least one physical and/orchemical variable within said body of water.

According to a third aspect of the present invention there is providedmeasurement means configured to measure at least one physical and/orchemical variable in a body of water, said measurement means including,a housing, and at least one sensor mounted at least partially withinsaid housing, said sensor being configured to measure at least onephysical and/or chemical variable, wherein said measurement means isconfigured to be towed in said body of water at a predetermined depthwhilst simultaneously measuring, at least periodically, said least onephysical and/or chemical variable.

The measurement means can further include orientation means configuredto orientate said measurement means relative to an apparent currentexperienced by said measurement means when said measurement means isbeing towed. Preferably said orientation means includes at least onefin.

The measurement means can further include water intake means to allowthe collection of a sample of water from the body of water.

The measurement means can further include image capture means adapted togenerate a sequence of images of a region of said body of water adjacentto said measurement means, wherein in use the depth of the measurementmeans is controlled in response to the sequence of video images.

Preferably the at least one sensor is configured to measure one or moreof the following physical and chemical variables:

water depth, water temperature, conductivity, water turbidity, pH,dissolved oxygen, dissolved chloride, oxidation-reduction potential(ORP), soluble nitrate, ammonia, dissolved gases or chlorophyll A.

Preferably there is more than one sensor. Each sensor can measure one ormore physical and/or chemical variables.

Preferably said housing includes a frame.

Preferably said housing includes a water permeable container configuredto contain said at least one sensor.

The measurement means can further include data storage means incommunication with said at least one sensor, said data storage meansbeing configured to store measurement data generated by said at leastone sensor.

According to a fourth aspect of the present invention there is provideda system for taking a series of measurements of at least one physicaland/or chemical variable in a body of water, said system including:

measurement means configured to measure at least one physical and/orchemical variable in a body of water, wherein in use said measurementmeans is configured to be towed in said body of water at a predetermineddepth whilst simultaneously measuring, at least periodically, said atleast one physical and/or chemical variable to generate measurementdata; and

location means configured to determine the location of the measurementmeans while taking said measurements of the at least one physical and/orchemical variable to generate location data; and

data storage means configured to store said measurement data andlocation data.

Preferably the system includes depth control means configured to controlthe depth of the measurement means while said measurement means is beingtowed.

Preferably the system includes image capture means adapted to provide asequence of images of a region of the body of water adjacent themeasurement means.

Preferably the system includes water inlet means, mounted on saidmeasurement means, configured to allow collection one or more watersamples from the body of water.

Preferably the at least one measurement means is configured to measureone or more of the following physical or chemical variables:

water depth, water temperature, conductivity, water turbidity, pH,dissolved oxygen, dissolved chloride, oxidation-reduction potential(ORP), soluble nitrate, ammonia, dissolved gases or chlorophyll A.

The present invention also provides a dataset including a plurality ofmeasurements obtained according to the method described above, and a maprepresenting such a dataset.

The present invention additionally provides a map generated according tothe mapping method of described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1A shows the side view of an apparatus according to an embodimentof the present invention;

FIG. 1B shows a front view of the apparatus shown in FIG. 1A;

FIG. 2 shows a schematic representation of a system adapted to perform amethod according to an embodiment of the present invention;

FIG. 3 shows a flowchart depicting a method of mapping a body of wateraccording to an embodiment of the present invention;

FIG. 4 shows a map of a lake created from an exemplary output of thesystem, showing bottom depth contours vs. dissolved oxygen contours;

FIG. 5 shows a closer view of a region of FIG. 4;

FIG. 6 shows another part of the same lake as that shown in FIG. 4,bottom depth contours are mapped against conductivity contours;

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1A shows a side view of an measurement means or instrument pack 10which is adapted to be towed underneath a boat in a body of surfacewater, such as a lake, in order to take measurements of one or morewater quality variables. The instrument pack or sled 10 includes of aninstrument housing, or stack 20, which is centrally mounted within asupporting frame 50. The frame 50 comprises a pair of vertically mountedgenerally trapezoidal outer frames 30 with a horizontally disposedrectangular frame member 31 along its top side. The frame 50additionally includes vertically and horizontally disposed supportmembers 60, 65 and 55 respectively to provide additional strength to theframe 50. FIG. 1B, which depicts a front view of the sled 10, shows thehorizontal support members 55 spaced between the pair of trapezoidalframe members 30.

The sled 10 additionally includes a fixed rudder 70, which comprises avertically oriented generally flat plate. The rudder 70 acts as a vaneto orientate the sled 10 when in use. The sled 10 additionally includesa plurality of lifting eyes 80 from which the sled 10 is suspended whenin use.

The sled 10 is adapted to carry various sensors and instruments whichcan be used to map bodies of surface water. The stack 20 comprises acylinder of perforated PVC pipe inside which is housed one or moresensors used by the measurement means to take measurement of physical orchemical variables. In a preferred embodiment the sensor(s) looselymounted within the stack 20 to provide shock absorption. Further shockprotection for the sensor(s) can be provided by a layer of protectivepadding, such as foam rubber or the like, which can be mounted betweenthe sensor(s) and the inner wall of the stack 20.

Sensors can be provided which measure parameters such as water depth,water temperature, pH, dissolved oxygen, dissolved chloride,conductivity, oxidation-reduction potential and water turbidity. Asuitable sensor for measuring each of these parameters is manufacturedby the Hydro Lab Corporation of Austin, Texas. An integrated unit, knownas the “Sonde”, contains the sensors for each of the above mentionedparameters. However, it will be appreciated by a person skilled in theart that other suitable sensors are available, and many other waterquality, or physical variables can be measured.

In addition to the stack 20, which houses the sensors the sled 10 hasmounted on it a lamp 22 and video camera 24, which both face ingenerally forward direction. Preferably, the lamp illuminates an ark ofaround 120 degrees and produces illumination of sufficient intensity toproduce a visibility of 6 meters or more at a water depth of 50 meters.

Additionally, a section of hose 19 or pipe is mounted adjacent to thestack. The hose 19 has a valve 19B at its bottom end and a connectionmeans 19A at its top end. In the use, the hose segment 19 is connectedto a pump and filter system via a main hose or conduit (not shown), andcan be used to pump water to the surface from adjacent the sensors, inorder to take water samples.

Turning now to FIG. 2 which shows an exemplary embodiment of a systemincluding a sled 10 as described above, adapted to take measurementsand/or generate multi-variable maps of a body of surface water.

The system 200 is comprised of two portions. The first, or on boardportions 210 comprises all necessary equipment required to record andtrack data produced by the sensors, collect water samples, and allowpractical operation of the system. The so called “on board” portion 210of the system 200 is thus named as it is generally mounted on board avessel such as a boat, or barge, or the like.

The second portion, termed the “under water portion” 220 is comprised ofthe sled, sensors and monitoring equipment mounted thereon, as describedin connection with FIGS. 1A and 1B.

Turning now to the on board portion, 210 of the system 200. The on boardcomponents 210 include the following equipment:

-   -   A boom winch 230. The boom winch 230 is used to raise and lower        the sled 220 as required. Preferably, the boom winch is adapted        to lift the sled entirely clear of the water and on board the        tow vessel, where the sled can be securely stowed.    -   Winch drive 235. The winch drive 235 is of a commonly known type        and acts to reel in the sled via the boom 230.    -   A data acquisition system 240. The data acquisition system        collects and records data from the sensors mounted on the sled,        and additionally stores navigation information such as the tow        boat's position and other appropriate parameters such as the        time a reading is taken. The data acquisition system 240 will in        general be a computer including a central processing unit and        data storage device.    -   A video monitor 250. The video monitor 250 displays images        captured by the camera mounted on the sled 220. The images        displayed on the monitor are used by the system operator to        ensure that the sled does not collide with any objects in its        path and to ensure that the sled is maintained at a suitable        separation from the floor of the body of surface water being        mapped. Additionally, the images captured by the camera can be        recorded for later visual analysis of the floor of the body of        surface water being mapped if required.    -   Navigation DGPS 260. A differential global positioning system        (DGPS) and antenna is mounted on the tow vehicle to provide        accurate monitoring of the path of the tow vehicle. The data        from the navigation DGPS 260 is sent to the data acquisition        system and recorded along side simultaneously taken measurements        of one or more water quality variables to generate a data set.    -   Pump 270 and filter 275. The pump 270 and filter 275 are used to        obtain samples of water from a position along side the sled. The        pump 270 is kept in fluid communication with the sled via a        conduit hose 272. In order to obtain a sample the pump is        activated and water is pumped from the sampling site. Prior to        collection as a sample the water is filtered to remove any large        particles using filter 275. In order to avoid having to prime        the pump before each sample is taken a foot valve is located on        the bottom most end of pipe 272 to maintain a column of water        within the pipe 272.    -   Generators 280 and 282. Generators 280 and 282 provide the        required electrical power for the various on board components        and under water components of the system 200. In the embodiment        shown in FIG. 2 two separate generators 280, 282 are shown,        first being a 240 volt AC generator 282 for suppling power to        the data acquisition system and video monitor, and the second        being a twelve volt DC generator 280 for suppling power to the        boom winch 230 and the pump 270.

The operation of a system of the type disclosed in FIG. 2 in a processfor taking a series of measurements of one or more water qualityvariables, and the creation of a map plotting such water qualityvariable will now be described in connection with FIGS. 3 to 6.

In a first step 310 of the method 300 the tow craft is manoeuvred to asuitable position on the body of water to be mapped, to begin collectingdata of the physical variable of interest. The tow craft will typicallybe a speedboat or barge, or the like, and will have mounted on it the“on board” components 210 of the system of FIG. 2. Initially the towcraft additionally carries the sled 220 and associated sensors andmonitoring devices as described above. Once the tow craft is in positionthe sled 220 can be lowered into the water using boom winch 230 to aposition as shown in FIG. 2. The sled 220 is in communication with thedata acquisition 240 and video monitor 260 of the system 200 via datacables, 273, 274 respectively. Fluid communication with pump 270 ismaintained via conduit 272 so that water samples can be taken asrequired.

In most applications a predetermined vertical position in the lake willbe chosen, at which to take measurements of the variable of interest.For example, if the chosen vertical position is a this may be at aparticular depth, say ten meters, the results obtained and map producedwill show a horizontal cross-section of a variable in the lake at thechosen depth. Alternatively, the vertical positioning of the sled may bedetermined with reference to the bottom of the body of water for examplemeasurements can be taken adjacent the bottom of the body of water. Insuch a situation, the sled 220 is lowered until it is adjacent to, butnot touching the bottom of the body of water. It has been found thatmeasurements of the concentration of various substances or physicalvariable at the bottom of a body water can be measured by maintaining aseparation of approximately one meter between the sled and the bottom ofthe body of water.

Once the sled 220 is submerged to the desired depth the data collectionprocess 330 can be begun. The data collection process 330 includes threeprocesses, which are preformed substantially simultaneously.

In the data collection process 330 the sled 220 is towed beneath the towcraft, such that the predetermined vertical position of the sled ismaintained (step 350). If measurements are to be taken at a particulardepth no adjustment of the depth of the sled will be required, unless anobstacle is encountered during the measurement run. However, if the sledis to be maintained a set distance, say one meter, above the floor ofthe body of the water the boom winch (230 of FIG. 2) is used to raiseand lower the sled 220 such that the desired separation between the sledand the floor of the body of water is maintained. In order to allow thesled 220 to be maintained at the correct vertical position using theboom winch, (230 of FIG. 2) video images from a camera mounted on sled220 are displayed on a monitor 250. The person operating the winch drive235 is able to view the region of the body of water adjacent to the sled10 and operate the boom winch to raise the sled 220 clear of anyobstacles in its path, or lower the sled so that the desired separationbetween the sled and the floor of the body of water is maintained.

It should be noted that the fixed rudder (feature 70 of FIGS. 1A and 1B)acts to orientate the sled 220 such that the front of the sled 220always points in an “upstream” direction, that is in the direction oftravel of the sled and tow craft, if no current is present, or into theperceived water flow, if a cross current acts on the sled. By ensuringcorrect orientation of the sled, the video camera mounted on the sledalways points in the direction of motion of the sled, thereby allowingthe driver of the boom winch to see any obstacles as the sled approachesthem.

In order to allow the winch driver sufficient time to lift the sledclear of any obstacles in its way, the tow craft should tow the sled ata suitable speed. If the tow speed is too high there is a danger thatthe boom winch will not be able to raise the sled quickly enough inorder to clear any obstacles in its path. If the tow speed is too low anon-optimal amount of data will be collected during a tow run.Additional parameters which affect the optimal speed at which to tow thesled include, the time required for the sensors mounted on the sled 220to reach equilibrium with the surrounding water, and the need tomaintain a sufficient correlation between the position of the sled andthe towing craft. If a high tow speed is used the sled will lag behindthe tow craft by a greater distance and the position of the boatdetermined by the DGPS system will not be representative of the positionof the sled 220. By adding ballast to the sled 10 the distance the sledlags behind the tow craft towed can be reduced. Thus in areas of highcurrent ballast can be added to the sled ensure that the sled 10 is notswept too far away from the tow-craft. If the current is relatively slowunnecessary ballast can be removed.

As will also be appreciated by a person skilled in the art the sledshould be towed slowly enough for its sensors to come into equilibriumwith the surrounding water before making each measurement, otherwiseaccurate measurements of water quality variable will not be achieved.Typically a speed of around 2 km/h is suitable for taking measurements.

With the sled being towed at the desired depth, measurements of waterquality can be taken (step 360.) Preferably, measurements of more thanone water quality variable are taken simultaneously. In step 340 theposition of the tow craft is determined using the global positioningsystem, thus producing a data set representing the measurement locationand one or more water quality variable. This process can be repeated,thereby building up a data set of water quality measurements andcorresponding position readings.

At any particular point of interest the tow craft may be stopped (step370) and water samples taken from the site. The water samples are takenby using pump 272 to pump water up conduit 272 and through a filter,prior to collection. Advantageously conduit 272 attaches to a length ofhose (e.g. 19A of FIG. 1) on the sled which is fitted with a foot valve19B, thereby allowing a column of water to be maintained in the conduit272, and removing the need to prime pump 272 before taking each watersample. Once a water sample is taken (step 365) the tow craft and sledcan be repositioned and further water samples taken (step 375.) Thisprocess may be repeated either during the measurement run (process 330)or separately.

Once all measurements are taken the sled 380 can be lifted out of thewater and back into, a stowed position on the tow craft (step 380.)

At this point all of the data has been collected and a map can begenerated (step 390) using suitable computer software. Preferably, atopographic map is overlain onto the region being surveyed. Typically amap of the area which has been surveyed has overlayed on to it, incontrasting colours, additional contours or regions shaded to depict theconcentration, intensity or variation in the measured physical orchemical variable. It is preferable that the topographic information isderived from water depth readings from the measurement means. Howeverother sources such as the towing boat's depth finder or even availablehydrographic charts can be used to obtain the necessary topographicalinformation.

As discussed above a system and method according to the presentinvention, can accumulate data along the bottom of a body of water, atintermediate depth in the body of water, or along lines of constantbearing. Existing software programs are available (such as “Surfer”)which are adapted to translate data so collected into contour maps,cross-section maps, three dimensional maps or correlation graphs of twoor more of the measured variable. Maps and graphs may also be preparedbased on the analysis of water samples taken during a sampling run.

FIGS. 4 to 6 show exemplary maps, which can be produced using a system,and method as described above. FIGS. 4 and 5 show portions of LakeTemagami, which is a lake of around 70 kilometers in length located innorthern Ontario, Canada. FIG. 6 shows a portion of Cross Bay, which islocated on Lake Temagami.

Turning firstly to FIG. 4 which shows bottom depth contours versesdissolved oxygen contours for a segment of Lake Temagami around TemagamiIsland. In this map 400 (and FIGS. 5 and 6) the horizontal axis 410represents longitude in degrees west, and the vertical axes 420represents latitude in degrees north. The line of crosses 401 representsthe path taken by the tow vehicle whilst the sled is taking measurementsof the water quality variable. Each cross eg. 402 represents ameasurement point along the path of the tow craft. The total length ofthe track shown in FIG. 4 is around 15 kilometers.

The depth contours of the body of water are shown by the lines e.g. 403and 404 with the 20, 40, 50, 60 and 80 foot depth contours beinglabelled eg. 421, 440, 450 and 460 respectively. Land masses, such asthe lake shore and islands eg. Temagami Island 475 are shown as whiteregions without topographical contours.

The shading from light to dark grey which is overlayed onto thistopographical information of the lake bottom represents dissolved oxygenas a percentage of saturation with air. Scale 409 shows the percentagesaturation which each shade of grey represents. In an alternativeembodiment the shades of grey can be represented in colour or as asecond set of contours overlain on the topographic contour information.

The dissolved oxygen contours between the adjacent measurement paths areinterpolated values calculated by mapping software. In parts of the mapin which only a single path is present the dissolved oxygen contours areonly accurate in the immediate vicinity of the path as the measurementstaken by the sled are only representative of the variable values at thepoint at which the measurement is taken rather than over some largervolume. Thus, in places of interest such as that shown in FIGS. 5 alarge number of measurements are taken in a small area to build up anaccurate picture of the measured physical or chemical variable(s) in theregion of interest.

Turning now to FIGS. 5 which shows a close up view 500 of a smalldissolved oxygen anomaly 499 located at latitude 46.96° and longitude80.030° in FIG. 4.

In FIG. 5 the points at which measurements were taken using themeasuring device are marked with crosses 501 and the dissolved oxygencontours are mapped over the topographical contours eg. 510, 520 aspreviously described in connection with FIG. 4. From FIG. 5 it can bedetermined that a correlation exists in this position between depth anddissolved oxygen. This suggests that ground water is erupting in thedeepest part of the lake in this immediate area.

FIG. 6 shows a similar map to that shown in FIGS. 4 and 5. However, FIG.6 shows a segment of Cross Bay, and plots topographic contours, againstconductivity contours measured in millisiemens. Again the horizontalaxis 610 represents longitude in degrees west, and the vertical axes 620represents latitude in degrees north. The line of crosses 601 representsthe path taken by the tow vehicle whilst the sled is taking measurementsof the water quality variable. Each cross eg. 602 represents ameasurement point along the path of the tow craft. Depth contours of thebody of water are shown by the lines eg. 603 and 604 with the 50 and 100foot depth contours being labelled eg. 650 and 651 respectively.However, the land masses, such as the lake shore and islands are shownas white regions with topographical contours in this example.

The scale 630 shows the correlation between shading and conductivity.This map 600 shows that there is not a strong correlation between depthand conductivity in this lake.

As will be appreciated by a person skilled in the art various analysescan be performed using graphs of different water quality variables ormeasures of physical variables. For example, from FIG. 5 it may beascertained that in this part of the lake there is an erupting groundwater supply with lower concentration of dissolved oxygen than in thesurrounding lake water.

Embodiments of the present invention can be used to take measurementsand create maps of bodies of standing surface water such as lakes,ponds, lagoons, harbours, tidal estuaries and, with variousmodifications the continental shelf Within such bodies of water theinvention can be used to identity such occurrences as sources oferupting ground water, sources of contaminants or pollutants, and tracetheir spread in three dimensions throughout the body of water; identifychemical reactions produced by such contaminants introduced into thewater. Embodiments of the invention can be used to identify circulationpatterns in the standing body of water; the flow rate and volume ofcontaminants introduced into the body of water and locate sources ofcontaminants in the water.

Embodiments of the system and method as described above is particularlyuseful in environmental assessment monitoring and surveying. In largebodies of water such a system and method may be used to determine waterquality over the entire body in a quick and efficient manner.Furthermore, such a system may be advantageously employed in mineralexploration. For example, ground water traversing an unknown ore depositwill pick up a distinct chemical signature which may be identified, andthe source detected through subsequent ground water discharge into astanding body of water. In combination with geological surveying andother operations the location of the ore deposit can be determined. Anembodiment of the system and method could also be used to locatedsources of fresh ground-water erupting from the continental shelf Suchsources of ground-water may then be tapped to supply fresh water toremote costal communities near-by. will be understood that the inventiondisclosed and defined herein extends to all alternative combinations oftwo or more of the individual features mentioned or evident from thetext or drawings. All of these different combinations constitute variousalternative aspects of the invention.

The foregoing describes embodiments of the present invention andmodifications, obvious to those skilled in the art can be made thereto,without departing from the scope of the present invention.

1. A method for measuring at least one physical and/or chemical variableat a plurality of different locations within a body of water, saidmethod including the steps of: providing dynamic measurement meansconfigured to measure at least one physical and/or chemical variable;towing said measurement means in said body of water at a predetermineddepth, and simultaneously taking measurements of least one physicaland/or chemical variable, at least periodically, and generatingmeasurement data; and determining the location of the measurement meanswhile taking said measurements of the at least one physical and/orchemical variable and generating corresponding location data.
 2. Amethod as claimed in claim 1 which includes the additional step of:controlling the depth of the measurement means in said body of waterwhilst towing said measurement means.
 3. A method as claimed in claim 2which includes the additional step of: detecting obstacles in a regionadjacent to said measurement means; and wherein the step of controllingthe depth of said measurement means is performed in response to detectedobstacles.
 4. A method as claimed in claim 3 in which the step of,detecting obstacles in a region adjacent to said measurement means,includes the sub-steps of: providing image capture means on saidmeasurement means, adapted to generate a sequence of images of a regionadjacent to said measurement means; and visually detecting saidobstacles from said sequence of images.
 5. A method as claimed in claim1 wherein said measurement means includes water intake means configuredto collect water from said body of water and wherein said methodincludes the additional step of: collecting at least one water samplefrom said body of water through said water intake means.
 6. A method asclaimed in claim 2 wherein the predetermined depth is determinedrelative to a bottom of the body of water.
 7. A method as claimed inclaim 1 wherein water depth and at least one other physical and/orchemical variable is measured by said measurement means.
 8. A method asclaimed in claim 1 wherein at least one physical and/or chemicalvariable measured by the measurement means is selected from a listincluding the following physical variables: water depth, watertemperature, conductivity, and water turbidity.
 9. A method as claimedin claim 1 wherein at least one physical and/or chemical variablemeasured by the measurement means is selected from a list including thefollowing chemical variables: pH, dissolved oxygen, dissolved chloride,oxidation-reduction potential (ORP), soluble nitrate, ammonia, dissolvedgases or chlorophyll A.
 10. A method of mapping at least one physicaland/or chemical variable in body of water, said method including thesteps of: providing dynamic measurement means configured to measure theat least one physical and/or chemical variable; and towing saidmeasurement means in said body of water at a predetermined depth, andsimultaneously taking measurements of said at least one physical and/orchemical variable, at least periodically, and generating measurementdata; determining the location of the measurement means while takingsaid measurements of the at least one physical and/or chemical variableand generating corresponding location data; and generating a maprepresentative of the distribution of at least one physical and/orchemical variable within said body of water on the basis of the locationand measurement data.
 11. A method as claimed in claim 10 including theadditional step of: determining the depth of the measurement means whenmeasuring said at least one physical and/or chemical variable, andgenerating measurement depth data, and wherein said map is generated onthe basis of the measurement depth data, measurement data and locationdata.
 12. A method as claimed in claim 11 which includes the additionalstep of: controlling the depth of the measurement means in said body ofwater whilst towing said measurement means.
 13. A method as claimed inclaim 12 which includes the additional step of: detecting obstacles in aregion adjacent to said measurement means; and wherein the step ofcontrolling the depth of said measurement means is performed in responseto detected obstacles.
 14. A method as claimed in claim 13 in which thestep of, detecting obstacles in a region adjacent to said measurementmeans, includes the sub-steps of: providing image capture means on saidmeasurement means, adapted to generate a sequence of images of a regionadjacent to said measurement means; and visually detecting saidobstacles from said sequence of images.
 15. A method as claimed in claim10 in which said measurement means includes water intake meansconfigured to collect water from said body of water and wherein saidmethod includes the additional step of: collecting at least one watersample from said body of water through said water intake means.
 16. Amethod as claimed in claim 10 wherein the predetermined depth isdetermined relative to a bottom of the body of water.
 17. A method asclaimed in claim 10 wherein water depth and at least one other physicaland/or chemical variable is measured by said measurement means.
 18. Amethod as claimed in claim 10 wherein at least one physical and/orchemical variable measured by the measurement means is selected from alist including the following physical variables: water depth, watertemperature, conductivity, and water turbidity.
 19. A method as claimedin claim 10 wherein at least one physical and/or chemical variablemeasured by the measurement means is selected from a list including thefollowing chemical variables: pH, dissolved oxygen, dissolved chloride,oxidation-reduction potential (ORP), soluble nitrate, ammonia, dissolvedgases or chlorophyll A.
 20. A method as claimed in claim 10 which themap represents topographic contours of a body of water and thedistribution of the at least one physical and/or chemical variablewithin said body of water.
 21. A measurement means configured to measureat least one physical and/or chemical variable in a body of water, saidmeasurement means including, a housing, and at least one sensor mountedat least partially within said housing, said sensor being configured tomeasure at least one physical and/or chemical variable, wherein saidmeasurement means is configured to be towed in said body of water at apredetermined depth whilst simultaneously measuring, at leastperiodically, said least one physical and/or chemical variable.
 22. Ameasurement means as claimed in claim 21 which further includesorientation means configured to orientate said measurement meansrelative to an apparent current experienced by said measurement meanswhen said measurement means is being towed.
 23. A measurement means asclaimed in claim 21 wherein said orientation means includes at least onefin.
 24. A measurement means as claimed in claim 21 which additionallyincludes water intake means to allow the collection of a sample of waterfrom the body of water.
 25. A measurement means as claimed in claim 21which additionally includes image capture means adapted to generate asequence of images of a region of said body of water adjacent to saidmeasurement means, wherein in use the depth of the measurement means iscontrolled in response to the sequence of video images.
 26. Ameasurement means as claimed in claim 21 wherein said at least onesensor is configured to measure one or more of the following physicalvariables: water depth, water temperature, conductivity, waterturbidity.
 27. A measurement means as claimed in claim 21 wherein saidat least one sensor is configured to measure one or more of thefollowing chemical variables: pH, dissolved oxygen, dissolved chloride,oxidation-reduction potential (ORP), soluble nitrate, ammonia, dissolvedgases or chlorophyll A.
 28. A measurement means as claimed in claim 21wherein said housing includes a frame.
 29. A measurement means asclaimed in claim 21 wherein said housing includes a water permeablecontainer configured to contain said at least one sensor.
 30. Ameasurement means as claimed in claim 21 which further includes datastorage means in communication with said at least one sensor, said datastorage means being configured to store measurement data generated bysaid at least one sensor.
 31. A system for taking a series ofmeasurements of at least one physical and/or chemical variable in a bodyof water, said system including: measurement means configured to measureat least one physical and/or chemical variable in a body of water,wherein in use said measurement means is configured to be towed in saidbody of water at a predetermined depth whilst simultaneously measuring,at least periodically, said at least one physical and/or chemicalvariable to generate measurement data; and location means configured todetermine the location of the measurement means while taking saidmeasurements of the at least one physical and/or chemical variable togenerate location data; and data storage means configured to store saidmeasurement data and location data.
 32. A system for taking a series ofmeasurements as claimed in claim 31 which further includes depth controlmeans configured to control the depth of the measurement means whilesaid measurement means is being towed.
 33. A system as claimed in claim31 including image capture means adapted to provide a sequence of imagesof a region of the body of water adjacent the measurement means.
 34. Asystem as claimed in claim 31 which further includes a water inletmeans, mounted on said measurement means, configured to allow collectionone or more water samples from the body of water.
 35. A system asclaimed in claim 31 wherein said at least one measurement means isconfigured to measure one or more of the following physical variables:water depth, water temperature, conductivity, water turbidity.
 36. Asystem as claimed in claim 31 wherein said at least one sensor isconfigured to measure one or more of the following chemical variables:pH, dissolved oxygen, dissolved chloride, oxidation-reduction potential(ORP), soluble nitrate, ammonia, dissolved gases or chlorophyll A.
 37. Adataset including a plurality of measurements obtained according toclaim
 1. 38. A map representing a dataset as claimed in claim
 37. 39. Amap generated according to the method of claim 10.